Setting and checking DC offset on output (needs to be very close to zero) is an integral part of the bias procedure with F5.
Bias and offset are interlinked, it’s all part of the whole to set the amplifier’s operating point.
Bias and offset are interlinked, it’s all part of the whole to set the amplifier’s operating point.
Ok I bought myself another multimeter today.
Whats most important, that the offset is near zero or is it important that the 2
output transistors are the same (0.6v and 0.6v) or can one be 0.6v and the other 0,5v if offset is zero?
Whats most important, that the offset is near zero or is it important that the 2
output transistors are the same (0.6v and 0.6v) or can one be 0.6v and the other 0,5v if offset is zero?
Transistors will only rarely be identical, as there is lots of (normal) variation in Vgs between the NPN and PNP mosfets. Get them as close as you can, with minimum (hopefully zero) offset.
I now have about zero offset,the transistors are at 0,6v and 0,495v(over the 0,47 ohm resistors)Is it okay??
It is okay. DC offset is what’s important.
I suspect the white resistor is not quite the same value as the green…
I suspect the white resistor is not quite the same value as the green…
Is there any specific phase relation for the secondary windings of the mains transformer for quiet operation? I have a faint buzz on my F5 outputs.
rotating Donut to find sweet spot ( minimal hum) is standard practice
if you have Donut with CT arrangement, anything connected out of phase will give either Dodo amp or BigBadaBoom
if you have Donut with each secondary having own bridge, secondary phasing is irrelevant
if you have Donut with CT arrangement, anything connected out of phase will give either Dodo amp or BigBadaBoom
if you have Donut with each secondary having own bridge, secondary phasing is irrelevant
Hello gentlemen. I will be building an F5 and will need some help from you. I'm a lifelong DIYer but this is my first foray into amp building (I've built a Crack and a WHAMMY but they're pretty begginer level kits). Also I'm not an EE and have zero experience with circuits.
I'm buiding the vanilla version but would like to do things the "best" way. I won't bother you with questions unless I've done my research first. Thank you in advance.
So, first is the PSU caps. From I've been able to find, the first set of C basically just needs to have high ripple current. From the F5 manual, current draw is 1.6A so roughly 3X that (call it 6A) should be ok? For the second C set, esr is more important. Also, what is a realistic temp these guys will be exposed to? I understand that the heatsinks will be ~ 50C and the amp itself does 180W but how does that translate to cap temp? Should I be too concerned with 105 vs 85 temp caps?
Thank you!
I'm buiding the vanilla version but would like to do things the "best" way. I won't bother you with questions unless I've done my research first. Thank you in advance.
So, first is the PSU caps. From I've been able to find, the first set of C basically just needs to have high ripple current. From the F5 manual, current draw is 1.6A so roughly 3X that (call it 6A) should be ok? For the second C set, esr is more important. Also, what is a realistic temp these guys will be exposed to? I understand that the heatsinks will be ~ 50C and the amp itself does 180W but how does that translate to cap temp? Should I be too concerned with 105 vs 85 temp caps?
Thank you!
don't fret
just buy first adequate snap-in caps at Dig or Mou or wherever
shoot for decent CRC , say 22mF-0R1-22mF
voltage 25V min, 35V even better
caps - proper Manufacturer ; you'll most likely find CDE easiest (Cornel Dubilier never was bad)
if possible, shoot for 105C caps, if not - 85C is good with proper case ventilation
just buy first adequate snap-in caps at Dig or Mou or wherever
shoot for decent CRC , say 22mF-0R1-22mF
voltage 25V min, 35V even better
caps - proper Manufacturer ; you'll most likely find CDE easiest (Cornel Dubilier never was bad)
if possible, shoot for 105C caps, if not - 85C is good with proper case ventilation
then buy Black Gate, and cry next 3 years waiting for burn-in........ to finally hear some music
@deltavektor
I had some low level hum in my stereo amp, but making it mono blocks completely eliminated the hum from both channels. If all else fails, dual power supplies might resolve it.
@A Jedi
Don't go insane with caps. The DIYaudiostore boards use 8 caps, and with that many all you need is decent, not exceptional, ripple current. I think the Nichicons I used were like $15 each. Not crazy expensive. The idle power doesn't have much of anything to do with ripple demands. The amp may momentarily draw a LOT more than 1.6 amp from the power supply driving a 4 ohm speaker with a 3 ohm low point. Using more caps in parallel gets you higher ripple current and lower ESR with cheaper parts.
I had some low level hum in my stereo amp, but making it mono blocks completely eliminated the hum from both channels. If all else fails, dual power supplies might resolve it.
@A Jedi
Don't go insane with caps. The DIYaudiostore boards use 8 caps, and with that many all you need is decent, not exceptional, ripple current. I think the Nichicons I used were like $15 each. Not crazy expensive. The idle power doesn't have much of anything to do with ripple demands. The amp may momentarily draw a LOT more than 1.6 amp from the power supply driving a 4 ohm speaker with a 3 ohm low point. Using more caps in parallel gets you higher ripple current and lower ESR with cheaper parts.